Study finds link between early life antibiotic exposure and weight gain in children

A pioneering study conducted within a nationwide network, the National Patient Centered Clinical Research Network (PCORnet), finds that antibiotic use at <24 months of age was associated with slightly higher body weight at 5 years of age. The study, "Early Life Antibiotic Use and Weight Outcomes in Children Ages 48 to <72 Months of Age," appears in the journal Pediatrics published online on October 31.

Antibiotic overuse has been a major population health concern, primarily due to the dangers of increasing antibiotic resistance but, recently, interest in antibiotics' effect on weight has emerged. Antibiotics disrupt the natural balance of intestinal bacteria or gut microbiome. Because the microbiome has important effects on the body's metabolism and how food is digested, researchers have hypothesized that changes in weight might occur with microbiome disruptions. This issue is important for parents and their doctors, who often must decide whether children should receive antibiotics.

PCORnet is an innovative research network that facilitates research across healthcare institutions through use of a process whereby each institution organizes their data from electronic health records into a common form. The network also uses a variety of important innovations to protect patient privacy. Studies conducted in PCORnet also incorporate patient views in the design and conduct of the study.

Previous studies have had conflicting results regarding the potential effect of antibiotics on weight. This new study is the largest to tackle the issue, involving a sample of over 360,000 children from 35 institutions across the country. Researchers examined the relationship between antibiotic use among children less than two years old and their weight at around five years old, analyzing such factors as: diagnosis of chronic conditions, number of antibiotic prescriptions given to children, and the specific types of antibiotics given.

Results demonstrate that the effect of antibiotic use in early childhood and weight around age 5 was small -- less than a pound difference in weight for children of average height and weight receiving 4 or more courses of antibiotics, compared to children who received none. "While this small difference in weight might not be important for individual decisions regarding antibiotic prescribing by doctors and parents, these data may serve, in a small way, to further encourage efforts to decrease antibiotic use. The ability to conduct research on large, diverse populations in networks like PCORnet provides critical opportunities to examine important research questions, no matter the outcome." says Jason Block, lead author and Associate Professor of Population Medicine at the Harvard Pilgrim Health Care Institute and Harvard Medical School.